The present invention relates to a fastening device for fastening a tube to a bearing structure, particularly a horizontal mesh frame tube of a mesh cage attached to a transport pallet that is used to hold a liquid container, wherein in order to form the fastening device the tube has a fastening section with a zone that has been flattened by compression, the zone being provided with a fastening hole to accommodate a fastening bolt connecting the fastening section to the bearing structure, wherein the fastening hole has a perimeter shaped such that the hole perimeter defines a force application plane between a bolt head and the fastening section that is inclined at an angle α relative to a fastening plane in which the fastening section is connected to the bearing structure. The present invention also relates to a method for producing such a fastening device and a transport and storage container for liquids that is equipped with such a fastening device.
Fastening devices of the type described in the introduction are particularly used to secure mesh cages in liquid transport and storage containers, also called IBCs, in which the mesh cage serves to hold and protect a liquid container that is made from plastic and disposed on a transport pallet. Since the inner container of an IBC is often used for holding toxic or chemically aggressive liquids, the reliability of the fastening device is of particularly high importance.
In order to secure the mesh cage on the transport pallet, a lower, horizontally extending mesh frame tube is attached to the transport pallet via fastening means of the type described in the introduction. To ensure that the mesh cage or the lower horizontal frame tube may be fastened to the transport pallet from outside the mesh cage, the known fastening devices are designed such that the fastening bolts, which usually have the form of fastening screws, may be screwed with an outwardly inclined fastening or bolting axis through a fastening hole formed in the fastening section and into a base of the transport pallet. To this end, an inner section of the perimeter of the fastening hole is curved away from a fastening plane defined by the pallet base of the transport pallet, while an outer section of the hole perimeter is located in the fastening plane, so that a defined bearing surface is created for the bolt head of the fastening screw both on the inside and the outside despite the fact that the bolting or screwing axis is inclined towards the outside. In this context, the screw head is braced only by a circular collar in the area of the inner hole perimeter section, and consequently if the screw is subjected to excessively high tightening torque or unfavourable operating loads, such as may occur when an IBC is being handled, a bending moment is exerted on the screw head, which in extreme cases may cause the part to fail due to breakage of the fastening screw, or the screw head may be sheared off.
This in turn may lead to damage that renders the IBC unusable, and thus considerable financial losses may be suffered as a result of the failure of a fastening device, and if the inner container is damaged by the failure of the component, the liquid held in the inner container may also escape, causing corresponding harm to the environment.